問題詳情

78. A company has two electric generators. The time until failure for each generator follows an exponential distribution with mean 10. The company will begin using the second generator immediately after the first one fails.
Calculate the variance of the total time that the generators produce electricity.
(A) 10
(B) 20
(C) 50
(D) 100
(E) 200

參考答案

答案:E

統計:A:0,B:0,C:0,D:0,E:0

難度:計算中